1. Field of the Invention
This invention relates to a grout impregnation method and more particularly to a method for impregnating two-part curable grout, for example a composite grout comprising water glass and carbonated water or carbon dioxide gas, into soil to stabilize the earth.
2. Related Arts
In an early grout impregnation method, a single-liquid grout was used. Thereafter, various improvements have been introduced into this method. For example, two liquids, which are curable when they react each other, are used as a grout (two-part curable grout) in such a manner that they are mingled in a Y-shaped pipe provided at a base portion of an injection tube. Recently, a further improvement has been made and a method has become predominant in which the two liquids are mingled and mixed within the injection tube and the resulted grout is injected into the earth.
Although various kinds of two-part curable grouts have been known, a grout containing water glass (sodium silicate) is most widely used today because it does not pollute the soil. Water glass may be used with a reactant such as an acid or a salt of the acid.
Water glass may alternatively be used with a reactant of carbonated water to provide a grout to be impregnated into the earth for stabilization of the soil. This is disclosed, for example, in Japanese Kokai No. 53-74709.
Carbon dioxide gas has such an advantage that it is less expensive and harmless. However, to prepare carbonated water by absorbing carbon dioxide gas in water and to use the resultant carbonated water with water glass as a grout, there is a problem to be solved as will be described later. By this reason, this grout has not been put into practical use heretofore.
Such a reaction is given by: EQU 2H.sup.+ +CO.sub.3.sup.2- +Na.sub.2 O nSiO.sub.2 .fwdarw.Na.sub.2 CO.sub.3 +H.sub.2 O+nSiO.sub.2
Thus, when carbonated water and water glass are impregnated into the soil after their mixing, silica and sodium carbonate are produced in the soil to solidify flimsy portions of the earth, stabilizing the same.
In the conventional grout impregnation using a two-part curable grout, it has been considered essential to mix the two liquids supplied in equal amounts under equal pressures. The conventional grout impregnation of this type, in effect, is carried out by mixing the two liquid-parts of equal amounts under equal pressures.
However, when carbonated water is preliminarily prepared and supplied to the injection tube, carbonated water is liable to be separated into water and carbon dioxide gas if the pressure within the tube is not high enough, and can not be reacted sufficiently with water glass. On the other hand, when it is required to prepare carbonated water at an execution site, water and carbon dioxide gas must be contacted under a high pressure in a closed vessel to obtain carbonated water of high concentration. By this reason, carbonated water should inevitably be led to the injection tube under a high pressure. In addition, the pressure within the dissolving vessel for preparing carbonated water should be increased to shorten a gelling time of the grout as shown in FIG. 10.
If carbonated water is thus supplied into the injection tube under a high pressure and water glass is supplied thereinto under a lower pressure, the flow of carbonated water become dominant within the tube and the two liquids are not reacted sufficiently.
A valve provided after the mixing of two liquids has been known. However, the known valve after the mixing of the liquids is a check valve for preventing back flow of soil into the injection tube after injection of the grout into the soil, and not a valve for holding a pressure of the mixing section. A valve is not provided, in a conventional technique, upstream the mixing section.